Fluid-blast circuit interrupters with two selectively-operated fluid-blast sources



June 21, 1966 w. M LEEDS 3,257,533

FLUID-BLAST CIRCUIT INTERRUPTERS WITH TWO SELECTIVELY-OPERATED FLUID-BLAST SOURCES Filed April 23, 1965 3 Sheets-Sheet 1 LI fan Fig. I. 24\

- 2 MAGNETIC 36 MATERIAL 4| '1 I3 INVENTOR Winrhrop M. Leeds Fig.4. 50%

ATTORNEY w. M. LEEDS 3,257,533 BLAST CIRCUIT INTERRUPTERS WITH TWO SELECTIVELY-OPERATED June 21, 1966 FLUID FLUID-BLAST SOURCES 3 Sheets-Sheet 2 Filed April 23, 1965 I I I I I I I I f I I! III l/ll/l/l/l/l/ll/l/l/ Ill/lll/f/l/l/l/l Ill/l 1/4 June 21, 1966 w. M. LEEDS 3,257,533

FLUID-BLAST CIRCUIT INTERRUPTERS WITH TWO SELECTIVELY-OPERATED FLUID-BLAST SOURCES Filed April 25, 1965 3 Sheets-Sheet 3 D FAULT F BREAKER LOAD C SYSTEM 8 T BREAKER BREAKER GROUND SYSTEM SYSTEM BREAKER A 1 SYSTEM LOAD BREAKER SYSTEM BREAKER SYSTEM LOAD BREAKER BREAKER SYSTEM SYSTEM BREAKER SYSTEM LOAD FIG. 6 70 7| CT\A A A v v BLAST VALVE 84 7 49' 72 92 82 I 7 l 85 73 PROTECTIVE SYSTEM 87 as 75 5 5 l 29 NORMAL so 8| EXTINGUISHING MEANS United States Patent 3 257 533 FLUID-BLAST CIRCI JIT INTERRUPTERS WITH TWO SELECTIVELY-OPERATED FLUID-BLAST SOURCES Winthrop M. Leeds, Forest Hills, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 23, 1965, Ser. No. 452,451 7 Claims. (Cl. 200-448) This application is a continuation-in-part of my copending application filed July 20, 1961-, Serial No. 125,506.

This invention relates to circuit interrupters in general, and, more particularly, to circuit interrupters adaptable for interrupting medium-value and also relatively highpower circuits.

A general object of the present invention is to provide a highly effective and economical circuit interrupter suitable for the interruption of currents over a wide range of values.

A more specific object of the present invention is to provide an improved circuit interrupter of the puffer type, that is one injecting a quantity of arc-extinguishing gas into the contact structure by the operation of a piston structure; and preferably, supplementary means are additionally provided, selectively operated only during highcurrent interruptions, to force the injection of a liquefied gas into the arc region to assist in the interruption of highamperage fault currents.

In puffer-types of circuit interrupters, such as those set forth in United States patent application filed March 24, 1961, Serial No. 98,135, now U.S. Patent 3,214,544, issued October 26, 1965, to Winthrop M. Leeds, and assigned to the assignee of the instant application, the advantage is obtained that the device is relatively cheap to manufacture, and reliance need not be placed upon an associated compressor for providing a dual-pressure operating system. As a result, the operation of such puffertype circuit interrupters is relatively simple and is entirely satisfactory for moderate-value currents. However, as the interrupting currents increase in magnitude, the puttertype breakers require unreasonably high operating forces. Another form of circuit interrupter, not using a puffer, which has been tested successfully interrupting over 40,000 amperes is a liquid sulfur-hcxafluoride (SP injector type, such as set forth in United States patent application filed September 13, 1957, Serial No. 683,760, now U.S. Patent 3,150,245 issued September 22, 1964 to Winthrop M. Leeds and Benjamin P. Baker, and assigned to the assignee of the instant application. However, this latter-mentioned circuit interrupter requires a high-cost compressor to take the low-pressure exhaust gas and recompress it into a liquid, and force it back into the accumulator.

Accordingly, it is a further object of the present invention to provide an improved circuit interrupter utilizing a puffer-type of interrupter for normal operations, and only during the high short-circuit current interrupting operations is there brought into play a selectively-operated valve device which will function to inject an additional quantity of a liquefied gas, such as liquefied sulfur hexafluoride (SP gas, into the arcing region to quickly bring about the interruption of such high-value short-circuit currents.

It is an additional object of the present invention to provide an improved circuit interrupter of the type set forth in the immediately preceding paragraph, in which the operation of the normally-functioning piston is rendered inoperable during such high short-circuit current interruptions, and an associated valve structure. is employed to prevent dissipation of the liquefied gas pressure by preventing the compressed gas from entering the piston chamber.

The circuit interrupter described in this invention shows two sources of gas blast to accomplish arc quenching. One of these, for instance a puffer piston, provides gas flow, preferably of SP suflicient to extinguish arcs in a range up to moderate current values of several thousand amperes. A second source, consisting of a reservoir containing fluid under high pressure in either the gaseous or liquid state, is selectively, controlled to come into action only when high currents above the range handled by the first source are to be interrupted.

Prior art, such as Ruppel Patent Re. 21,125, broadly covers the above-described selective action interrupter. However, the Ruppel structure, and other devices providing interrupting action initiated directly by overload current magnitude,'sutfer from the disadvantage that the high pressure blast is released whenever high overload current flows through the breaker regardless of whether or not the protective system has called for this particular breaker to be tripped.

My invention specifically avoids this undesirable situation by using a current-responsive element which does not produce a gas blast directly as by opening a valve, but rather sets up conditions under overload that will cause the high pressure fluid blast to be activated if and only if the breaker is actually tripped. The construction shown involves current-initiated magnetic means for aligning a cam-operating surface with the cam line of action so that the opening movement of the breaker will operate the auxiliary blast valve on high current'overload conditions only. If the breaker is not tripped, no blast occurs even though high current actuates the cam alignment device.

Other arrangements will suggest themselves to those skilled in the art for producing similar results of energizing a second source of fluid blast only when a condition of high current overload exists together with opening movement of the breaker contacts as a result of a tripping signal being applied during the overload condition.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

FIG. 1 is a side elevational view of a circuit interrupter embodying features of the present invention;

FIG. 2 is a longitudinal vertical sectional view taken through the tank structure of the circuit interrupter of FIG. 1 with the contact structure illustrated at an intermediate point in the opening operation, the putter structure shown rendered inoperable, and the liquefied gas injector being illustrated in its operable position;

FIG. 3 is a fragmentary sectional view taken substantially along the line IIIIII of FIG. 2; 1

FIG. 4 is an end elevational view of the circuit interrupter;

FIG. 5 illustrates diagrammatically a radial type distribution system; and,

FIG. 6 illustrates a modified type circuit interrupting arrangement.

Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral 1 generally designates a circuit interrupter particularly adaptable for interrupting a wide range of currents. As shown, the circuit interrupter 1 generally comprises a tank structure 2 into which downwardly extend a pair of terminal bushings 3, 4. As viewed in FIG. 2, the lower ends of the downwardly-extending terminal bushings 3, 4 support, in a fixed position, an interrupting assembly generally designated by the reference numeral 5.

The interrupting assembly 5 generally includes a perforated tubular movable contact 6 cooperable with a relatively stationary contact structure 7 comprising a plurality of finger contacts 8. As shown more clearly in FIG. 3, the finger contacts 8 are circumferentially disposed and engage the outer surface of the movable contact 6 in the closed-circuit position.

As shown in FIG. 2, the movable contact 6 is secured to an operating rod 9 fixedly secured to a yoke member 10 of generally T-shaped configuration. Secured by bolts 11 to the yoke member 10 is a pair of insulating operating rods 12, 13 which abut at their right-hand ends a movable piston 14, operable within a piston cylinder 15 secured to the lower extremity 4a of the right-hand terminal bushing structure 4.

Preferably, the movable contact structure, generally designated by the reference numeral 16, and comprising the movable contact 6 and operating rods 12, 13, is biased in a leftward opening direction by a contact accelerating spring 17. To effect rightward closing movement of the movable contact structure 16 and consequent compression of the contact accelerating spring 17, there is provided an insulating operating rod 18 pivotally connected, as at 19, to a lower portion 20 of the yoke member 10. The insulating operating rod 18 is pivotally connected, as at 21, to a rotatable crank-arm 22 keyed to an operating shaft 23, which passes through a sealed opening provided in a depending operating crank housing 24 associated with the tank structure 2. The seal provided along the operating shaft 23 may be of the type set forth in United States Patent 2,889,434 issued June 2, 1959, to Harry I. Lingal, and assigned to the assignee of the instant application.

From the foregoing description it will be apparent that clockwise rotative movement of the crank-arm 22, as effected by an external operating mechanism, not shown, providing motive power through the operating shaft 23, will effect rightward closing movement of the movable contact structure 16 effecting thereby contact closing engagement between the movable tubular contact 6 and the relatively stationary contact structure 7 compressing the accelerating spring 17 and driving the puffer piston 14 toward the right, meanwhile effecting compression of the piston driving spring 25. The breaker will then be in the closed-circuit position and is preferably latched in this position by the externally-situated operating mechanism.

To effect an opening operation of the circuit interrupter 1, the external mechanism, not shown, is unlatched, and the contact accelerating spring 17 is immediately effective to quickly cause leftward opening movement of the movable contact 6 away from the relatively stationary contact structure 7, drawing an are 26 therebetween, which quickly moves by virtue of the gas blast, to the arcing born 27 and along the inner surface 28 of the movable tubular contact 6 as shown in FIG. 2. The manner of interruption is more fully set forth in United States patent application filed October 7, 1960, Serial No. 61,284, now US. Patent 3,154,658 issuedOctober 27, 1964, to Robert G. Colclaser, In, and Russell N. Yeckley, and assigned to the assignee of the instant application.

Simultaneously, with leftward opening movement of the movable contact 6, there occurs leftward driving motion of the puffer piston 14, biased by the piston driving spring 25, and a consequent blast of compressed gas, such as sulfur-hexafiuoride (SF gas, through a valve structure 29 associated with a mixing chamber 30. In other words, the driving spring will force the puffer piston 14 to the left compressing thereby gas within the region 31 and opening the valve structure 29 thereby causing the ejection of gas under pressure into the mixing chamber and along the drawn are 26 in the manner illustrated by the arrows 32 in FIG. 2.

The foregoing interrupting structure utilizing the puffer piston 14 is suitable for moderate value currents, say up to 10,000 amperes. However, at infrequent intervals, there occurs the existence of a heavy short-circuit current on the line, and fault currents over 10,000 amperes may be encountered. Thus, currents for high interrupting power, say above 20,000 amperes, may come into existence. To provide a puffer action which would be adequate to effect the interruption of these high-amperage currents would require excessive spring pressure for the piston driving spring 25. It is, therefore, an additional purpose of the present invention to provide a supplementary interrupting device 33 comprising a quantity of liquefied gas under pressure. When sulfur hexafluoride (SP gas is used under a'pressure of say 30 to 45 p.s.i. within the interior 34 of the tank structure 2, supplementary means consisting preferably of liquefied sulfur hexafiuoride (SP gas is contained within a pressure bottle 35 disposed externally of the tank structure 2 and connected therewith by means of an insulating conduit 36.

With reference to FIG. 2, it will be noted that disposed withinn-the pressurized bottle 35 is a piston 37 forced downwardly by nitrogen (N gas under pressure, say of the order of 800 to 1000 psi. The liquid SP accumulator 35 with nitrogen above the piston separator compressed to about 800 p.s.i. (well above the SP vapor pressure to prevent vapor lock) would be located outside the breaker tank, as shown in FIGS. 1 and .4 to make the pressure gauge 33 and liquid-level indicator 39 visible. In addition, the refilling plug 40 would be readily accessible.

With reference to FIGS. 2 and 3, it will be noted that encompassing the relatively stationary contact structure 7 is a split magnetic ring 41 having associated therewith an armature 42. The armature 42 is pivotally connected, as at 43, to a cam sleeve 44, which is biased by a helical spring, not shown, in a counterclockwise direction, as viewed in FIG. 3. Associated with the cam sleeve 44 is a cam lug 45 which, at times, makes abutting engagement with a valve cam follower 46, constituting one end of a valve actuating lever 47. With reference to FIG. 2, it will be noted that clockwise rotation'of the valve actuating lever 47 about its pivot 48 will effect opening of the valve 49 associated with the accumulator 35 and permit an injection of liquefied gas 50 into the mixing chamber 30. The injection of the liquefied gas 50 into the mixing chamber 30 will quickly effect closure of the piston valve structure 29, thereby moving the valve plate 51 over the associated apertures 52 and prevent the entrance of the gas into the piston cylinder region 31 of the operating cylinder 15. If this were allowed to occur, there would result some loss of effective pressure of the injected liquefied gas.

The armature 42, which causes the cam lug 45 to align with the cam follower 46, is so arranged as to be attracted and operable when current magnitudes, say of 10,000 amperes or over, flow through the contact structure 6, 7. As well known by those skilled in'the art, the passage of current through the relatively stationary contact structure 7 will cause an encompassing magnetic flux to flow through the split magnetic ring 41. Due to the air gap at 53, the armature 4-2 will be attracted, and will cause rotation of the cam sleeve 44 into an aligned position so that the cam lug 45 and valve cam follower 46 will make abutting engagement.

It will be apparent that following an interrupting operation the cessation of current through the contact structure 6, 7 will immediately permit the helical cam sleeve spring, not shown, to effect a retraction of the armature 42 and a consequent non-alignment position of the cam sleeve 44 relative to the valve cam follower 46. As a result, during a subsequent closing operation, there will be no opening of the valve structure 54 associated with the accumulator 3 5.

Puffer-type circuit interrupters utilizing sulfur-hexafiuoride (SP gas are self-contained, that is, contain no compressor and high-pressure reservoir, and therefore are preferred as economical design for moderate power highvoltage breakers. For high interrupting power (above 20,000 amperes, for example), puffer breakers require unreasonably high operating forces. Another form of interrupter', not utilizing a puffer, which has been tested successfully interrupting over 40,000 amperes is a liquid SP injector type. However, this requires a high-cost compressor to take the low-pressure exhaust gas and recompress it into a liquid and force it back into the accumulator.

The present invention is particularly concerned with a puffer-type breaker for normal load-switching duty, which is provided with a liquid sulfur-'hexafluoride SP6 accumulator tank and a valve arrangement 54, whereby liquid SP is injected into the interrupting chamber 30 only when short-circuit current flows through the breaker contacts 6, 7 during a tripping operation. Since short-circuit conditions only occur at rare intervals, the amount of liquid SP stored is sufficient for many'years service, and it may be replenished as needed at normal maintenance periods.

The interrupting device 1 illustrated in FIG. 2, shows an embodiment of the invention in which the interrupter assemblage 5 is suspended from a pair of bushing terminals 3, 4 inside a grounded steel tank 2. An insulating operating rod 18 is used to close the breaker by moving a tubular moving contact 6 into contacting engagement with a stationary finger cluster 7. At the same time, an accelerating spring .17 at the left-hand end of the assembly 5 is compressed, while on the right the puffer piston 14 is moved back compressing its driving spring 25. For normal lowpower switching duty, when the breaker is tripped, the accelerating spring 17 drives the moving contact 6 to the left, and an are 26 appears at the separating contacts 6, 7. The puffer piston 14 is also driven to the left, displacing SP gas through the check valve 29 and deionizing the arc 26,.which has moved to the arcing horn 27 and the inside 28 of the tubular moving contact 6. The gas exhausts to a chamber 56 on the left terminal 3, then passes up the hollow conductor 3a to the bushing cap 3b, where it is filtered and return to the tank 2. This filtering feature is set forth and claimed in United States patent application field March 217, 1961, Serial No. 98,632, now US. Patent 3,214,553, issued October 26, 1965, to Winthrop M. Leeds, and assigned to the assignee of the instant application.

The liquid SP accumulator 3 5 with nitrogen (N gas, above a piston separator 37, compressed to about800 p.s.i. (well above the SP vapor pressure to prevent vapor lock) would actually belocated outside the breaker tank 2, as shown in FIG. 1, to make the pressure gauge 38,

liquid-level indicator 39 and refilling plug 40 accessible.

A strong glass-reinforced insulating tube 36 would bring the liquid SP to the cam-operated valve 54 on the interrupter assembly 5. v

The cam is attached to a cylindrical sleeve 44 free to rotate about operating rod 12, but retained lengthwise to move with the piston-retrieving operating rod 12. A helical spring (not shown) keeps the cam 45 normally at such an angular position that reciprocating movement of the operating rod 12 will not operate the valve .54. A split ring 41 of magnetic material surrounds the stationary finger cluster 7. When current above a predetermined value, say 10,000 amperes, flows through the contacts 6, 7, the flux across the air gap 53 pulls the armature 42 down. The armature 42 is coupled to the cam sleeve 44 so that it will rotate the cam lug 45 in line with the follower 46 attached to the liquid SP valve 54 and still not impede longitudinal movement of the operating rod 12 and the cam sleeve 44, Thus, if short-circuit current exceeding the predetermined value flows through the contacts 6,.7 at the time the breaker 1 is tripped, the cam 45 becomes magnetically positioned so' that, as the contacts are opened, the cam follower 46 is actuated, opening the valve 54 momentarily to admit a quantity of liquid SP into the mixing chamber 30. Vaporization of this liquefied SP produces sufiicient gas pressure and flow that even high-current arcs are easily extinguished. Alternate arrangements for directing liquid spray into the are 26 are possible to speed up vaporization and intensify the cooling and deionization of the arc 26. The high pressure developed by the liquid SF closes the check valve 29 to prevent wasteful flow into the puffer cylinder 15 and possibly forcing back the puffer piston 14.

As soon as the current is interrupted, the cam-retrieving spring, not shown, moves back the cam surface 45 so that on the closing stroke, the liquid SP valve 54 will not be operated.

FIG. 5 diagrammatically illustrates a radial distribution system. It will be noted that fault current flows through all four breakers A, B, C, and D, but only breaker D should be tripped, so that onlyvthe faulted section of the system would be disconnected, leaving power flowing to all the other sections. Thus, there is no need for over-current responsive valves in breakers A, B, and C to be turned on, since these three breakers should not have to be tripped.

If the fault were between breakers B and C, only breaker B should open, but not breakerA. In this case, only half of the system would have to be disconnected, with power left on the other half. Breaker A should trip only if the fault were on the bus section between breakers A and B.

In connection with the. radial distribution system of FIG. 5, and the desirability of selective tripping of breakers, reference may be had to Chapter 7 and Fig. 74 of the book entitled, Silent Sentinels, published by the Westinghouse Electric Corporation, copyright 1940, and the accompanying descriptive matter.

It will be noted that in accordance with the present invention, the circuit interrupter uses two sources of gas blast to accomplish arc quenching. One of these, for instance, a putter piston, provides gas flow, preferably of sulfur-hexafluoride (SP gas, sufficient to extinguish arcs in a range up to moderate current values of several thousand amperes. A second source, consisting ofa reservoir containing fluid under high pressure in either the gaseous or liquid state, is selectively controlled to come into action only when high currents above the range handled by the first source are to be interrupted. An important disadvantage of breakers of the prior art, such as set forth in Ruppel Reissue Patent 21,125, is that interrupting action is initiated directly by the overload current magnitude, and the high-pressure blast is released whenever high overload current flows through the breaker, regardless of whether or not the protective system has been called for this particular breaker to be tripped.

My invention specifically avoids this undesirable situation by using a current-responsive element, which does not produce a gas blast directly, as by opening a valve, but rather sets up conditions under overload that will cause the high-pressure fluid blast to be activated if, and only if, the breaker is actually tripped. The construction shown in FIG. 2 involves current-initiated magnetic means for aligning a cam-operating surface with the cam line of action, so that the opening movement of the breaker will operate the auxiliary blast valve on high-current overload conditions only. However, if the breaker is not tripped,

no blast occurs even though high-current actuates the cam alignment device.

Other arrangements will,suggest themselves to those skilled in the art for producing similar results of energizing a second source of fluid blast only when a condition of high-current overload exists, together with opening movement of the breaker contacts, as a result of a tripping signal being applied during the overload condition.

In the construction set forth in FIG. 2 it will be noted that the overload current magnetically aligns the cam plate 45 with the cam follower 46 to actuate the blast valve 49 upon the circuit interrupter being tripped open. Other arrangements for providing the same result will. be apparent to those skilled in the art. For example, in the modified-type circuit interrupter 70 of FIG. 6 of the drawings, it will be noted that the fault current passing through the transmission line 71 will actuate the current transformer CT and energize the solenoid device 72 to effect contact 75. This will condition the interrupter 70 so that should the protective system 77 call upon the circuit interrupter 70 to open, the energization of the circuit 80, 81, will energize not only the tripping solenoid 32, but, in addition, energize the actuating solenoid 84 closing contacts 84 to thereby effect through the circuit connections 85, 86, energization of the blast-value solenoid 3'7 and thereby open the blast valve 49' releasing a blast of the second auxiliary fluid source, which is only brought into play on the existence of overload or fault current conditions.

It will be noted in FIG. 6 that a normal, relatively lowcurrent extinguishing means 99, including a piston device 91, sends a normal relatively low-current fluid flow through a blast pipe 92. This is analogous to the pufler device 14, 15 of FIG. 2, which is normally used for loadcarrying operation of the breaker.

It will, from the foregoing, be apparent that the improved circuit-interrupting arrangements of the present invention condition the breaker in response to overload or fault conditions to cause the flow of fluid from the second auxiliary overload current source only when the breaker is actually tripped open. The mere passage of overload current through the breaker does not in and of itself effect opening of the overload current blast valve 49, 49. The arrangement is such as to merely condition the circuit interrupter so that only during an actual tripping operation is there brought into play the supplementary source of arc-extinguishing fluid.

From the foregoing description of the invention, it will be. apparent that there is provided an improved economical puffer-type or other type circuit interrupter in which auxiliary liquefied gas injector means 33, 49' are employed selectively operated only on currents above a predetermined magnitude. Since the auxiliary liquefied gas interrupter device 33 is employed only infrequently, it need not be replaced except at relatively long intervals of time when normal maintenance operations would take place.

Although there has been illustrated and described particular embodiments of the invention, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

I claim as my invention:

1. The combination in a puffer-type circuit interrupter of a substantially closed metallic grounded tank, a pair of terminal bushings extending into said grounded metallic tank, an interrupting assembly supported at least in part by said pair of terminal bushings, the interrupting assembly including a movable contact, a relatively stationary contact and a pair of spaced insulating operating rods for effecting separation of the same, a driving operating rod for effecting reciprocal movement of said pair of spaced insulating operating rods, a puffer cylinder supported by one of said terminal bushings and having a puffer piston movable therein, means biasing said puffer piston in a direction to force a blast of gas into the arc established between said relatively stationary and movable contacts, the ends of the spaced insulating operating rods abutting said puffer piston to charge the same during the closing .operation of the interrupter, an accumulator containing a liquefied gas, valve structure associated with said accumulator to release a blast of liquefied gas therefrom, check valve means associated with said puffer cylinder, and magnetic structure including a rotatable cam sleeve having a Cam g 50. e fecting ope ation of said valve structure for selectively operating said valve structure only at currents above a predetermined value.

2. A selective magnetically-actuated valve structure for a fluid-blast circuit interrupter including contact structure separable to establish an are, a split magnetic ring surrounding said contact structure, a movable armature,

a cam sleeve carrying a cam lug and pivotally connected to said movable armature, blast-valve releasing means, a blast valve lever carrying a cam lug, whereby currents above a predetermined magnitude passing through said contact structure will effect movement of the armature to bring the cam lug and the valve cam follower into alignment to effect releasing of said blast means.

3. A fluid-blast circuit interrupter including contact means for establishing an arc, a first normal fluid-extinguishing means for interrupting said are under normal load-carrying operation of the interrupter, a second auxiliary fluid-extinguishing means for interrupting said are only under predetermined fault-current interrupting conditions including a fluid control valve therefor, currentresponsive conditioning means responsive tothe current flow through said contact means and operable only at current values above a predetermined current magnitude for conditioning said control valve to render the latter capable of opening and thereby releasing a blast of fluid from said second auxiliary fluid-extinguishing means, operating means for mechanically opening said contact means, means for initiating operation of said operating means, and means responsive only to the activation of said last-mentioned means to effect actual opening of the conditioned control valve for obtaining fluid flow from said second auxiliary fluid-extinguishing means for fault-current interruption.

4. The combination of claim 3, wherein the initiating eans is a protective device individually associated with the particular circuit interrupter and only at selected times operated.

5. The combination according to claim 3, wherein the first normal fluid-extinguishing means is a puffer piston, and the second auxiliary fluid-extinguishing means includes a liquefied gas accumulator.

6. The combination of claim 5, wherein the currentresponsive conditioning means includes a split magnetic ring surrounding the contact means and a movable armature selectively responsive to currents above a predetermined current magnitude.

'7. The combination according to claim 5, wherein the current-responsive conditioning means includes magnetic structure associated with the contact structure for selective action.

References Cited by the Examiner UNITED STATES PATENTS RE. 21,125 6/1939 Ruppel 200148 1,334,645 3/1920 Bechoff 200148 1,852,614 4/1932 Johnson et a1. 20087 2,484,863 10/ 1949 Stillwell 200-87 3,033,962 5/1962 Friedrich et a1 200l45 3,095,490 6/1963 Cromer et al 200l48 3,150,245 9/1964 Leeds et a1 200 FOREIGN PATENTS 1,107,318 5/1961 Germany.

475,370 11/1937 Great Britain. 538,554 10/1931 Great Britain.

ROBERT S. MACON, Acting Primary Examiner. 

1. THE COMBINATIONIN A PUFFER-TYPE CIRCUIT INTERRUPTER OF A SUBSTANTIALLY CLOSED METALLIC GROUNDED TANK, A PAIR OF TERMINAL BUSHINGS EXTENDING INTO SAID GROUNDED METALLIC TANK, AN INTERRUPTING ASSEMBLY SUPPORTED AT LEAST IN PART BY SAID PAIR OF TERMINAL BUSHINGS, THE INTERRUPTING ASSEMBLY INCLUDING A MOVABLE CONTACT, A RELATIVELY STATIONARY CONTACT AND A PAIR OF SPACED INSULATING OPERATING RODS FOR EFFECTING SEPARATION OF THE SAME, A DRIVING OPERATING ROD FOR EFFECTING RECIPROCAL MOVEMENT OF SAID PAIR OF SPACED INSULATING OPERATING RODS, A PUFFER CYLINDER SUPPORTED BY ONE OF SAID TERMINAL BUSHINGS AND HAVING A PUFFER PISTON MOVABLE THEREIN, MEANS BIASING SAID PUFFER PISTON IN A DIRECTION TO FORCE A BLAST OF GAS INTO THE ARC ESBABLISHED BETWEEN SAID RELATIVELY STATIONARY AND MOVABLE CONTACTS, THE ENDS OF THE SPACED INSULATING OPERATING RODS ABUTTING SAID PUFER PISTON TO CHARGE THE SAME DURING THE CLOSING OPERATION OF THE INTERRUPTER, AN ACCUMULATOR CONTAINING A LIQUEFIED GAS, VALVE STRUCTURE ASSOCIATED WITH SAID ACCUMULATOR TO RELEASE A BLAST OF LIQUEFIED GAS THEREFROM, CHECK VALVE MEANS ASSOCIATED WITH SAID PUFFER CYLINDER, AND MAGNETIC STRUCTURE INCLUDING A ROTATABLE CAM SLEEVE HAVING A CAM LUG FOR EFFECTING OPERATION OF SAID VALVE STRUCTURE FOR SELECTIVELY OPERATING SAID VALVE STRUCTURE ONLY AT CURRENTS ABOVE A PREDETERMINED VALUE. 